Tetrabromobisphenol-A (TBBPA) is the largest volume brominated flame retardant in the world. Its widespread utility in reducing risks of fire from certain plastics is in part due to its economy. The low manufacturing cost is, in turn, due to processes in which salable methyl bromide (a valuable soil fumigant) is co-produced with the TBBPA.
Methyl bromide is now suspected as being a factor in the depletion of the earth's ozone layer. Severe restrictions on the sale of methyl bromide are imminent. To maintain low manufacturing costs, it would therefore be desirable to co-produce a different salable chemical with the TBBPA.
N-propyl bromide has gained interest in recent years as a degreasing solvent in the precision cleaning industry. Due to the present market that exists and growth projections for that market, a method to economically produce high quality n-propyl bromide is desired. The economics of both TBBPA and n-propyl bromide production for sale are both improved using the co-production techniques outlined herein.
Prior art methods of producing TBBPA with the concomitant reduction of methyl bromide typically involve brominating bisphenol A (BPA) in the presence of an aqueous C.sub.1 to C.sub.4 alcohol. Although an aqueous n-propanol solvent system has been utilized to form TBBPA, it has been shown to produce a TBBPA product of lower yield that is more difficult to wash compared to a TBBPA product formed in an aqueous ethanol solvent system.
Other prior art methods have utilized either an aqueous alcohol or a non-polar solvent in combination with an oxidizing agent to reduce the amount of alkyl bromides formed. However, none of the prior art found to date discloses the use of non-aqueous n-propanol as the sole solvent and that reaction conditions may be adjusted to maximize the production of salable n-propyl bromide.
A need therefore exists for a process for making TBBPA in which the economics support the continued worldwide use of this valuable product, but in which potentially harmful methyl bromide is not generated. The present invention addresses that need.